An array type ultrasonic transducer in which a plurality of elongated reed-shaped piezoelectric elements are one-dimensionally arranged is widely used in an ultrasonic diagnosis apparatus and the like. In order to attain the higher sensibility of the ultrasonic transducer, a configuration in which a stacked piezoelectric ceramics is used in the reed-shaped piezoelectric element is conventionally used. In a case of using the stacked piezoelectric ceramics, when the number of stacking is n, as compared with a case in which the same frequency is attained in a single layer, under an assumption that a driving voltage is constant, an electric field becomes n times. Thus, a transmitted sound pressure is improved to n times.
FIG. 12A and FIG. 12B show a schematic view of a conventionally-known ultrasonic transducer. FIG. 12A shows the perspective view of the ultrasonic transducer, and FIG. 12B shows its sectional view, respectively. A piezoelectric element 1 is configured as a stacked body in which piezoelectric layers 2 of two layers and electrode layers of three layers are alternately stacked. In the piezoelectric layer 2 of the two layers, their polarization axes are opposite to each other, and in the electrode layer of the three layers, the upper and lower layers serve as ground electrode layers 3b, and the central layer serves as a signal electrode layer 3a, and they are electrically connected to an earth pickup electrode 4 and a signal lead wire 5, respectively.
The ground electrode layer 3b is electrically connected to a side electrode 6 laid onto the side and guided to the lower surface of the piezoelectric element 1 and electrically connected to the earth pickup electrode 4, for example, with soldering, electric conductive adhesive and the like. Similarly, the central signal electrode layer 3a is also guided through the side electrode 6 to the lower surface of the piezoelectric element 1 and connected to the signal lead wire 5. An acoustic matching layer 7 for efficiently transmitting and receiving an ultrasonic wave is formed on the upper portion of the piezoelectric element 1. Also, a rear member 8 for holding the piezoelectric element arrangement and absorbing and attenuating the ultrasonic wave to be emitted to the lower portion of the piezoelectric element 1 is placed in the lower portion of the piezoelectric element 1.
When the one-dimensional array arrangement is formed, a division processing apparatus, for example, such as a dicing saw and the like, is used. Since the division processing apparatus is used to form a division groove that arrives at the rear member 8 from the acoustic matching layer 7, the elongated reed-shaped piezoelectric element 1 is formed in the shape of an array (for example, refer to the following patent document 1).
Since it is divided into the array shapes, the width of the side electrode 6 is made narrower, which results in a possibility that the influence of the processing causes the electric conductive state to be unstable or disconnect. Thus, the sure electric conductive state is required to be reserved. A method of preliminarily forming the reed-shaped piezoelectric element 1 after the division to form the side electrode 6 by using the longitudinal direction side is considered. However, a step of arranging the reed-shaped piezoelectric elements 1 is required. Hence, there is a fear that the arrangement is disturbed.
Also, not only in the one-dimensional arrangement array but also in the two-dimensional arrangement array, the configuration of employing the stacked piezoelectric ceramics is conventionally known. In the two-dimensional arrangement array in which the size of the piezoelectric element 1 is smaller than the one-dimensional arrangement array, the employment of the stacked piezoelectric ceramics provides the effect that the electric impedance of the piezoelectric element 1 is decreased. Thus, this is beneficial.
FIG. 13A and FIG. 13B show schematic views of a conventionally-known two-dimensional arrangement array ultrasonic transducer. FIG. 13A is the schematic view showing the structure of the piezoelectric element, and FIG. 13B shows the schematic view in which a plurality of piezoelectric elements are arranged, respectively. The piezoelectric element 1 is configured as stacking body in which piezoelectric layers 2 of three layers and electrode layers 3 of four layers are alternately stacked. In this case, in the electrode layer 3 of the four layers, the upper first layer and third layer serve as the ground electrode layers 3b, and the second layer and the fourth layer that is the lowest layer serve as the signal electrode layers 3a. 
Similarly to the piezoelectric element of the one-dimensional arrangement array, the elongated reed-shaped piezoelectric element 1 (FIG. 13A) is preliminarily formed, and on the two sides whose longitudinal directions are wide, an insulating layer 9 having a predetermined width is formed on the end surface portion of the electrode layer 3 that is not desired to be electrically connected on the side (for example, the signal electrode layer 3a of the second layer, when the ground electrode layers 3b of the upper first layer and third layer are desired to be connected), and the side electrode 6 is formed from thereon, and consequently, the ground electrode layers 3b of the two layers or the signal electrode layers 3a of the two layers are electrically connected.
The plurality of elongated reed-shaped piezoelectric elements 1 on which the side electrodes 6 are formed, respectively, are arranged in line at a predetermined interval in an x-direction as shown in FIG. 13B, and then a gap 10 between the adjacent piezoelectric elements 1 is filled and fixed by using a resin such as adhesive and the like, and then a plurality of division grooves 11 extending in a direction orthogonal to the longitudinal direction of the reed-shaped piezoelectric elements 1, the x-direction in FIG. 13B are formed in a y-direction by using a division processing apparatus, for example, a dicing saw and the like, and they are similarly filled and fixed, thereby forming a two-dimensional piezoelectric element arrangement (for example, refer to the following patent document 2).
Also, in the ultrasonic transducer of a frequency of MHz that is typically used in the ultrasonic diagnosis apparatus and the like, the width of the reed-shaped piezoelectric element 1 is between several 10 μm and several 100 μm, and an interval 10 between the piezoelectric element 1 and the piezoelectric element 1 is several 10 μm, and even the two-dimensional arrangement array has the similar dimensions.
In the case of the conventional two-dimensional arrangement array shown in FIG. 13B, at a step of arranging the elongated reed-shaped piezoelectric elements 1 in line at the predetermined interval 10, it is operationally difficult to arrange the piezoelectric elements 1 each having the width of several 100 μm in line at the gap of several 10 μm. Moreover, it is also difficult to carry out the work for filling the gap 10 with the adhesive and the like in the situation that the element arrangement is kept after the arrangement, and at the time of the working, there is a possibility that the element is slightly moved which results in a positional displacement.
Patent Document 1: Japanese Patent Application Publication H01-174199
Patent Document 1: Japanese Patent Application Publication H11-299779
However, the conventional configuration has a possibility that the disturbance in the element arrangement leads to the disturbance in the generated ultrasonic beam and leads to the drop in a resolution and the quality drop in an ultrasonic diagnostic image. Thus, this has a problem that, when the disturbance in the arrangement is severe, the adjacent elements are brought into contact with each other, which potentially causes the electrical short-circuit and the structural crosstalk.